DISEASES OF THE FETLOCK, AXKLK, AND FOOT. 41i) 



a healthy horn Iiy wliich the injury may he repaiivih Heavy cai't 

 horses are more often atVectetl than tliose of any other rhi.ss. 



Cauneii. — The essential ek'nient in tlie prodnetion of canker is tlie 

 parasite; consequently the disease may l)e called contagious. As in 

 all other diseases due to specific causes, howevei", the seeds of the dis- 

 order must tind a suitable soil in which to «;ro\v before they are 

 rejjroduced. It may he said, then, that the conditions which favor 

 the {^repartition of the tissues foi- a leception (d* the seeds of this 

 disease are simply predisposing causes. 



The condition most favorable to the development (d' canlcei- is 

 dampness — in fact, dami)ness seems indispensable to the existence 

 and growth of the parasite; the disea.se is rarely, if ever, seen in 

 high, diy districts, and is much more common in lainy than in dry 

 seasons. Filthy stables and muddy roads have lieen classed among 

 the causes of canker; but it is very doubtful whether these conditions 

 can do more than favor a preparation of the foot for the reception 

 of the disease germ. 



All injurit's to the feet, by exposing the soft tissues, may render the 

 animal su.sceptible to infection; but neither the injury nor the irrita- 

 tion and inllannnation of the tissiies which follow are sufficient to 

 induce the di.sease. 



For some unknown reason horses with lymphatic temperaments — 

 thick .skins, flat feet, fleshy frogs, lieavy hair, and ])articularly with 

 white feet and legs — are especially liable to canker. 



S)/mptonu<t. — Usually, canker is confined to one foot; but it may 

 attack two, three, or all of the feet at once; or, as is more connnonly 

 seen, the disease attacks first one then another, until all may have 

 been successively affected. When the disease follows an injury which 

 has expostvl the soft tissues of the foot, the wound .shows no tendency 

 to heal, but instead there is .secreted fi"om the inflamed parts a pro- 

 fu.se, thin, fetid, watery discharge, which gradually undermines and 

 destroys the surrounding horn, until a large j)art of the sole and frog 

 is di.sease<l. The living tissues are swollen, dark colored, and covered 

 at certain points with particles of new, .soft, yellowish, thready horn, 

 which are con.stantly undergoing maceration in the abundant liquid 

 secretion by which they aie immer.scd. As this secretion escapes to 

 the .surrounding parts, it dries and forms .snudl, chee.sv masses com- 

 posed of partly dried horny matter, exceedingly offensive to the sense 

 of smell. When the di.seasi' originates independently of an injury, 

 the fii'st evidences of the trouble are the offensive oloi- of the foot, 

 the liquid secivtion from the cleft and siiles of the frog, and the 

 rotting away of the horn of the frog and sole. 



In the earlier .stages there is no interference with 1<»( omotioM, but 

 later the foot becomes sensitive, particularly if thf animal is usrd on 



